In the year 2000, more than 36,000 people were killed in automobile collisions in the United States. (Traffic Safety Facts 2000, U.S. Department of Transportation, December 2001.) Automobile manufacturers are investigating methods to reduce both the number of fatalities and the severity of injuries resulting from such collisions. Among the more promising solutions are reversible restraints and pre-triggered airbags.
Reversible restraints are activated immediately before a crash to reduce the severity of occupant injury. As the name suggests, these restraints are also capable of being reset or reinstalled quickly and inexpensively compared to, for example, air bags. Examples of reversible restraints include pre-tensioning seatbelts, drop-down knee padding, active headrests, extendable bumpers, and vehicle-structure reinforcement. Pre-triggered airbags use collision velocity data to supplement information from acceleration sensors in vehicle to estimate the kinetic energy involved in the collision. With this information, the airbags may be deployed at the optimum inflation rate and pressure, thereby enhancing their effectiveness and safety. Airbags deployed under such conditions tend to be less dangerous to children and smaller adults. As used herein, reversible restraint systems and pre-triggered air bags are referred to collectively as “collision-mitigation measures.”
Although most agree that collision-mitigation measures would have a profound effect on minimizing the severity of collisions, such measures have been difficult to implement with reliability. Specifically, due to inaccuracies of commercially-available sensing systems, such as short-range radars (SRR), it is often difficult to adequately estimate the true location of an observed object, especially with respect its bearing value. It may require many observations over time in order to prepare an adequate estimate of the object's true location and velocity vector. Accordingly, there is great interest in developing a system which minimizes the number of available observations needed to make a deployment decision, while still satisfying certain quality-of-decision requirements. In particular, an imminent collision situation should be detected reliably and at the earliest possible time. Likewise, when an imminent collision situation does not exist, then the probability of falsely predicting an imminent collision should be very small. It is critical that such false positive indications are minimized since deploying collision mitigation measures mistakenly is not only inconvenient and may involve a cost to remediate, but also is distracting and thus potentially dangerous.
Therefore, there is a need for a detection system that indicates an imminent-collision not only with a high degree of accuracy with little or no chance of a false positive indication, but also quickly to provide sufficient time to effectively deploy the collision mitigation measures. The present invention fulfills this need among others.